The Federal Communications Committee (FCC) is an independent agency of the United States government that is charged with regulating all non-federal government use of the radio spectrum (including radio and television (TV) broadcasting), and all interstate telecommunications (wire, satellite and cable) as well as all international communications that originate or terminate in the United States. In 2008, the FCC issued rules approving the unlicensed signal operation in the unused TV channels (i.e., white space). However, this approved, unlicensed use is subject to protections set in place for the primary users of the TV band. The primary users of the TV band are ATSC/National Television System Committee (NTSC) transmitters, such as TV broadcasters, and licensed wireless microphones. The new rules allow wireless technologies to use the TV white space as long as the technology and any resulting signal transmissions do not interfere with the existing primary users. For purposes of this disclosure, the various devices that utilize such technologies to access this TV white space will be referred to as “white space devices,” “unlicensed devices,” or the like.
One of the technologies proposed for unlicensed use within the white space would enable high-definition (HD) wireless display via an ATSC-compatible signal transmitted over the TV white space. Such technologies are described in commonly-owned, co-pending U.S. patent application Ser. No. 12/547,834, entitled, “Local Broadcast of Data Using Available Channels of a Spectrum,” filed Aug. 26, 2009, the disclosure of which is expressly incorporated herein by reference in its entirety. An issue that may develop in such unlicensed transmitters is misdetection of the unlicensed, ATSC-compatible signals as a licensed, primary user. This misdetection could result in preventing other unlicensed devices from reusing that particular white space channel. Because the FCC rules provide for ATSC sensing at −114 dBm, the resulting “black out” area around the misdetected transmission could be quite substantial, leading to a poor frequency reuse pattern and inefficient use of available white space resources. For purposes of this disclosure, a black out area refers to a physical area that the FCC provides around the licensed primary users of the TV band in order to prevent signal interference by the unlicensed transmissions. These problems could become even more severe in areas where there is only limited white space available. In such case, other white space devices might not even find an empty channel in which to operate.